1. Field of the Invention
Viewing transparencies through a hand-held dark tunnel improves visibility of shadow detail. It is particularly useful viewing medical radiographs where dark portions are commonly juxtaposed to bright areas. The dark tunnel improves visibility of detail in the dark areas of any trans-illuminated material.
2. Description of the Prior Art
The retrieval of quality information from dark portions of medical radiographs can be life saving. Retrieval of information of microscopic details is difficult also, especially in dark areas. These two problems are encountered during x-ray film analysis. They represent important parts of proper patient diagnosis. Such problems are a nuisance that interrupt the flow of work and require extra steps. Such conflict results in medical legal risk for physicians interpreting medical radiographs, especially mammograms.
Various styles of magnifying lenses have long been used to enhance viewing for fine detail in medical radiographs and other trans-illuminated materials. A magnifier lens is a prior-art component of the invention device described herein.
Dark portions of transparencies will appear black under normal lighting conditions, but often contain both detailed and larger image forms which simply cannot be seen without special viewing conditions. Four approaches have been used to deal with this problem: 1. An extra film is taken with exposure altered to lighten the shadow areas; 2. A lower contrast film is produced, either by using a different kind of film or by altering exposure and/or processing techniques. This enables a greater range of image contrast -light and dark areas- to be squeezed into the visible gray scale. With greater contrast scale, contrast resolution suffers reducing the distinction of interfaces between nearby structures of similar shades of gray; 3. The intensity of light transmitted through the dark areas of the film is increased. A "bright light" is the traditional and most commonly used device for examining dark areas on the films, but it requires time consuming manipulation of film and light. A circus of hands, feet, films, magnifier lenses and bright lights can be inspired, especially if attempting to dictate the findings simultaneously. Intense heat associated with the bright light has damaged many a film; 4. Electronic image enhancements exist using either night-viewing photo multiplier devices or by digitizing the images and making them amenable to manipulation of brightness, contrast, magnification and central gray level. Expensive, cumbersome and impractical for now, soon digitization will become the most common solution to the problems described.
A fifth solution to the problem is presented as the background of the invention herein. By providing an environment where visual darkness adaptation is provoked biochemically in the retina and by reflex dilation in the pupil, exceedingly weak light intensities can be detected by the human eye to distinguish form and detail. We have all experienced this phenomenon each time we step from a brightly lit room into what at first seems the total darkness of night. We must wait a minute to see. Soon we dark adapt and can usually find enough light to see. Reflex pupil dilation is rapid. Biochemical changes in the retina take longer, but can be used to advantage in situations where the extra time required is important.
Visual darkness adaptation is important to viewing weakly trans-illuminated images. Such adaptation is a long standing tradition encountered in theaters, in TV rooms, at slide presentations and in x-ray reading rooms. It has been accomplished by turning lights down or off; or by throwing a dark shroud over the head and the viewing screen to exclude ambient light; or by placing opaque covers over bright portions of the viewing area (masking). Darkness adaptation is also traditionally applied to x-ray viewing. Commonly it is provoked by monocular viewing of dark parts of a transparency through an open ended opaque tunnel positioned such that the bright portions of the viewing area are excluded from the tunnel opening. Probably since the first radiographs were produced by Wilhelm Roentgen 100 years ago, dark x-ray images were viewed by looking with one eye down an opaque dark tunnel. The tunnel is most commonly fashioned by rolling up a handy nearby x-ray film into a tube.
Manufactured instruments have been produced over the years that take advantage of darkness adaptation and magnification for viewing transparencies. A few are binocular. A popular model of such an instrument exists for x-ray viewing, the Panascope Viewer (Andover, Conn.). Optics physics limits binocular magnification for viewing at a reasonable working distance to about 3.5 power.
The Panascope Viewer provides both magnification and darkness adaptation. It has a rectangular cross section. It is constructed from rigid durable plastic through-out. It is molded proximally only generally to conform to the face and nose to cover both eyes. Though quite helpful, the Panascope suffers from several deficiencies.
It is rigid.
Its rigid proximal end does not fit snugly against the face. Considerable light leaks in between the face and the proximal end of the Panascope. Such ambient light at least partially defeats darkness adaptation.
Also its distal end is rigid and the distal opening cannot be made smaller or shaped to fit the dark portions on the trans-illuminated images. Thus, it is usually impossible to exclude any bright areas which also lie within the Panascope field of view near the dark area of interest. The forced inclusion of these bright areas blinds the eye and prevents optimal darkness adaptation.
Its rigid, one piece construction makes it difficult to reach the deeply placed magnifying lens to clean it or change it to a different magnification strength or lens type.
Its hard plastic is resistant to paint or multicolor dye decoration. It clatters when it falls. Though a very tough plastic, it could break on impact on a hard floor.
Several objects and advantages of the present invention are:
(a) A new use of inexpensive pliable welder's goggle to provide a soft, light-tight fit for effective light exclusion of ambient light where the proximal end of the viewing tunnel contacts the face. At the distal surface, the existing goggle has a slidable mount intended to hold dark safety glass and permit changing and cleaning of this glass. The slidable mount is suitable for easily attaching and detaching a simple custom manufactured opaque rigid oval lens board on which a magnification lens is mounted. Suitable binocular and monocular magnification lenses currently exist. PA1 (b) Soft, elastic neoprene rubber/cloth laminate (wet suit material) is fabricated into an open ended opaque viewing cylinder. The neoprene laminate viewing cylinder uses its elastic properties to be stretch mounted over the perimeter of the oval lens board providing a continuous dark viewing tunnel formed by the goggle proximally and the neoprene cylinder distally, joined by the intermediate oval lens board. (a) and (b) describe a four part design whereby: PA1 (c) the opaque elastic neoprene laminate viewing cylinder can be attached and detached easily over the lens board perimeter. The alignment and length of the neoprene laminate viewing cylinder can be slidably adjusted over the lens board perimeter to match various magnification focal lengths and other desirable viewing conditions. Its distal opening can be folded into a cuff to further expand its versatility. PA1 (d) The distal end of the neoprene laminate viewing cylinder can be manually distorted from its baseline oval shape to conform to the shape of the dark area on the transparency excluding nearby bright areas which detract from human darkness adaptation. The magnitude of the viewing advantages provided by the distal aperture shaping means is difficult to perceive until personally experienced. PA1 (e) The neoprene laminate viewing cylinder is supplied in many patterns and colors and can be easily dyed or painted with multi color designs. PA1 (f) Being light in weight and imbued with a soft, non-slippery surface, the neoprene laminate viewing cylinder, lens board and welder's face goggle fall quietly and harmlessly onto hard surfaces. It is easy to pick up and easy to hold up. It can be hand held or mounted with a headband. PA1 (g) The removable neoprene laminate viewing cylinder and slidably removable lens board provide for ease in dismantling for lens cleaning or lens changing or for substitution of a special purpose high power lens described below. PA1 (h) The specialty high power lenses combine with the light shielding properties of the welder's goggle to permit darkness adapted viewing of slides, microfilm and microfiche while they lie against a simple light box bypassing the need for large microfilm projection viewers. PA1 (i) One or several different lenses or special viewing devices, each mounted on a separate lens board, can be quickly changed using the slidable attachment indigenous to the welder's goggle as currently manufactured. Since the goggle is suitable as it exists, manufacturing savings can be realized.
Further objects and advantages will become apparent from a consideration of the ensuing description and drawings.